1. Field of the Invention
This invention relates to a method of reactivating an automobile exhaust oxidation catalyst and particularly to the reactivation of a noble metal catalyst with a halogen-containing material.
2. Description of the Prior Art
U.S. Pat. No. 3,134,732 describes a method of reactivating a platinum hydroforming catalyst, platinum on alumina, by contact with oxygen to burn off deposits, then with gaseous halogen to reduce platinum crystallites, followed by reduction of the halogen content with hydrogen. The hydroforming function involves treatment of naphtha stock in the presence of hydrogen. Maximum temperature in hydroforming is usually only 1050.degree.F. U.S. Pat. No. 2,906,702 also describes the use of halogen to reactivate platinum hydroforming catalyst. This process is similar to the first except the halogen is washed out with water. However, none of these references discloses the reactivation of thermally deactivated noble metal catalysts which have been exposed to extremely high temperatures for prolonged periods, nor the reactivation of noble metal catalysts used for oxidation, and more specifically, automotive exhaust gas oxidation.